For most of Asia and the Pacific, the acquired immunodeficiency syndrome (AIDS) had not been identified prior to the late l 980s and the number of cumulative cases is still quite low (I). However, AIDS is now a public health emergency in Thailand, and many neighboring countries are also at high risk of epidemic spread of human immunodeficiency virus type (HIV-l) infection.For example, studies in Papua New Guinea (the largest and most populous of the Pacific island nations) indicate widespread high-risk sexual behaviors and high rates of sexually transmitted diseases, particularly ulcerative genital conditions. Vital baseline data are needed on the HIV-1 subtypes present in Southeast Asia and in countries, like Papua New Guinea, where health care delivery systems and high rates of syphilis and tuberculosis are comparable to those in sub-Saharan Africa. Also, the endemicity of human T-cell lymphotropic virus type I (HTLV-I) infection in some Melanesian populations in Papua New Guinea places such groups at added risk for HIV-1 infection because of the immunosuppressive and T-cell activation properties of HTLV-I.